Sky view, also referred to as sky view range, sky visibility, sky openness, sky visible factor, firmament visibility, terrain openness, and so on, specifically refers to a percentage of a visible sky range that can be reached by people's line of sight in city open spaces enclosed by buildings. It directly depends on development layout of city construction, and are directly associated with multiple factors such as the degree of comfort and visual and psychological anticipation of public activities in a city. Therefore, the sky view is an important factor reflecting open space quality in city planning.
Existing city planning schemes generally ignore spatial feeling from human eyes. This often leads to disordered open spaces in a city space, and some open spaces are overcrowded to cause decreased open space quality;                1) there is a lack of a quantitative index to reflect the spatial feeling from human eyes, causing a gap in visual and psychological anticipation of the public, and failing to embody the human-oriented principle in city construction and development;        2) the whole technical solution lacks global simulation and evaluation. City planning and development is a long-term process, and if there is no global simulation and evaluation, different areas in city construction may interfere with each other during the development, thus affecting the degree of comfort of public activities in a city.        
One of the important reasons is that there is no spatial experience, which is actually perceived from line of sight of human eyes, for simulation and analysis of the whole planning scheme. In particular, there is no evaluation factor and evaluation criterion for global simulation operation of the whole planning range.